(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Children's Library | Biodiversity Heritage Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "IS 15506: Gaseous Fire Extinguishing Systems--IG 55 Extinguishing Systems"

**************** 




Disclosure to Promote the Right To Information 

Whereas the Parliament of India has set out to provide a practical regime of right to 
information for citizens to secure access to information under the control of public authorities, 
in order to promote transparency and accountability in the working of every public authority, 
and whereas the attached publication of the Bureau of Indian Standards is of particular interest 
to the public, particularly disadvantaged communities and those engaged in the pursuit of 
education and knowledge, the attached public safety standard is made available to promote the 
timely dissemination of this information in an accurate manner to the public. 




Mazdoor Kisan Shakti Sangathan 
"The Right to Information, The Right to Live'' 



IS 15506 (2004, Reaffirmed 2010) : Gaseous Fire 
Extinguishing Systems--IG 55 Extinguishing Systems. ICS 
13.220.10 




Jawaharlal Nehru 
'Step Out From the Old to the New" 



aj^&vi iJii^s:y%K^ isb^^ni^seg 



:<>5&i| mT'5K^5?::5:^>^i»l 



K^^^iXSVCd^ 



Satyanarayan Gangaram Pitroda 
Invent a New India Using Knowledge 



Bhartrhari — Nitisatakam 
''Knowledge is such a treasure which cannot be stolen" 




^'^^^r 



k 




M^JT 3?f^ W^ Mc^fcl^l — ^fl^ 55 "^FR ^^^ 

Indian Standard 

GASEOUS FIRE EXTINGUISHING SYSTEMS — 
IG 55 EXTINGUISHING SYSTEMS 



18 15506:2004 

REAFFfRlVJED 



ICS 13.220.10 



©BIS 2004 

BUREAU OF INDIAN STANDARDS 

MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG 

NEW DELHI 110002 

August 2004 Price Group 5 



Fire Fighting Sectional Committee, CED 22 



FOREWORD 

This Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized by the Fire 
Fighting Sectional Committee had been approved by the Civil Engineering Division Council. 

The objective of this standard is to provide guidance to the users of IG 55 systems with specific 
requirements for the control of fires of Class A or Class B type. It does not cover the design of explosion 
suppression systems. 

It is important that the fire protection of a building or plant be considered as a whole. IG 55 total flooding 
systems form only a part, though an important part, of the available fire protection facilities. It should not be 
assumed that the installation of an IG 55 total flooding system necessarily removes the need to consider 
supplementary measures^ such as the provision of portable fire extinguishers or mobile appliances for first aid or 
emergency use, or measures to deal with special hazards. 

Controlled inert atmospheres are recognized as effective for extinguishing Class A and Class B fires where 
electrical risks are present. Nevertheless, it should not be forgotten, in the planning of comprehensive schemes, 
that there may be hazards for which this technique is not suitable, or that in certain circumstances or situations 
there may be danger in its use requiring special precautions. 



rS 15506 : 2004 



Indian Standard 

GASEOUS FIRE EXTINGUISHING SYSTEMS 
IG 55 EXTINGUISHING SYSTEMS 



1 SCOPE 

1.1 This standard sets out specific requirements 
for the design and installation of total flooding 
fire extinguishing systems employing 10 55 gas 
extinguishant. This standard is applicable to single 
supply as well as distributed supply systems. 

1.2 This standard complements various general 
requirements applicable to all types of gaseous fire 
extinguishing systems ( Halocarbon as well as 
Inert gas systems ) listed in IS 15493. As such, 
both these standards should be read together 
before designing a system. Where requirements in 
both the standards differ, this standard shall take 
precedence. 

1.3 Before using IG 55, nature of fire and fire spread 
shall be studied for suitability of extinguishment as 
high discharge time of 60 s may not be suitable for 
rapid spreading fires. 

1.4 This standard covers systems operating at 
normal pressure of 15 MPa at 21°C and 20 MPa 
at 2 PC only. 

2 REFERENCES 

The standards given below contain provisions, 
which through reference in this text, constitute 
provisions of this standard. At the time of publication, 
the editions indicated were valid. All standards are 
subject to revision and parties to agreements based 
on this standard are encouraged to investigate the 
possibility of applying the most recent editions of the 
standards indicated below: 

IS No. Title 

7285:1988 Specification for seamless steel 

cylinders for permanent and high 
pressure liquefiable gases ( second 
revision ). 

15493:2004 Gaseous fire extinguishing 

systems — General requirements 

3 GENERAL INFORMATION 

a) IG 55 total flooding system is designed to 
develop a controlled atmosphere in an 
enclosed space yielding a reduced oxygen 
concentration that will not sustain 
combustion. The appropriate IG 55 



concentration shall also be maintained 
until the temperature within the enclosure 
has fallen below the re-ignition point. 

b) The minimum IG 55 concentration necessary 
to extinguish a flame and the minimum 
oxygen concentration necessary to support 
combustion have been determined by 
experiments for several surface-type fires 
particularly those involving liquids and 
gases. For deep-seated fires, longer soaking 
times may be necessary but are difficult to 
predict. 

c) It is important that residual oxygen 
■ concentration are not only reached but also 

maintained for a sufficient period of time to 
allow effective emergency action by trained 
personnel. This is equally important in all 
classes of fire since a persistent ignition 
source can lead to a recurrence of the initial 
event once the IG 55 has dissipated. 

d) Nature of fire and fire spread shall be 
studied before hand for suitability of 
extinguishment for IG 55 as high discharge 
time of 60 s may not be suitable for rapid 
spreading fires. 

4 GAS CHARACTERISTICS AND PROPERTIES 

4.1 IG 55 is a colourless, odourless and electrically 
non-conductive gas with a density approximately the 
same as that of air. 

4.2 IG 55 gas is a mixture consisting normally of 
50 percent nitrogen and 50 percent argon ( both by 
volume ). The mixture specification of IG 55 gas is 
shown in Table 1. 

Table 1 Mixture Specification of IG 55 Gas 

{Clause A2) 



SI No. 


C onstituent 


Percentage Ran^c 


(1) 


(2) 


(3) 


i) 


Argon 


50±5 


ii) 


Nitrogen 


50 ± 5 



4.3 IG 55 system can be used for extinguishing 
fires of all classes within the limits specified 
in IS 15493. 

4.4 Components for IG 55 gas shall comply with the 
specification as shown in Table 2. 



IS 15506 : 2004 





Table 2 


Specification for IG 55 






(Clause 4A) 




SI No. 


Specification Argon 


Nitrogen 


(1) 


(2) 


(3) 


(4) 


i) 


Purity 


> 99.9 percent 
by volume, Min 


> 99.9 percent 


ii) 


Moisture 


< 10 ppm 


< 1 ppm 


iii) 


Oxygen 


< 10 ppm 


< 10 ppm 



4.5 Physical properties of IG 55 gas are shown 
in Table 3. 

Table 3 Physical Properties of IG 55 

(Clause 4.5) 

Value 

(3) 

33.95 

190.1 

199.7 

134.7 

4.15 
15.2 

0.708 



SI No. 

(1) 
i) 

ii) 
iii) 
iv) 

V) 

vi) 
vii) 



Property 

(2) 

Molecular mass 

Boiling point at 100 kPa, X 

Freezing point, °C 

Critical temperature, °C 

Critical pressure, MPa 

Vapour pressure at 2Q°C, MPa 

Specific volume of super-heated 
vapour at 0.1 MPa and 20°C 



4.6 Toxicological information for IG 55 gas are shown 
in Table 4. 

Table 4 Toxicological Information for IG 55Gas 

(Clause 4.6) 



SI No. 

(1) 
i) 



Property 



(2) 



Value 
Percent 

(3) 
43 



No observed adverse effect 
level (NOAEL) 

ii) Lowest observed adverse effect 52 

level (LOAEL) 

NOTE — These values are the functional equivalents 
of NOAEL and LOAEL values which correspond to 
12 percent, Min oxygen for the no-effect level and 
10 percent minimum oxygen for the low-effect level. 

4.7 Fill Pressure 

The fill pressure of the IG 55 cylinder shall not 
exceed the values provided in Fig. 1 for systems 
operating at 15 MPa bars and 20 MPa bars 
respectively. 

5 SAFETY OF PERSONNEL 

In addition to the provisions specified under 
IS 15493, the following requirements shall also 
apply. 



5.1 Protection of Occupants 

IG 55 total flooding systems shall not be used in 
design concentrations greater than 52 percent 
( corresponds to injected concentrations of 
74 percent ) in normally occupied areas, unless means 
are provided to ensure safe egress of personnel prior 
to the discharge of the inert gas mixture. 

5.2 In areas, where there is a likelihood of significant 
difference between gross and net volumes of the 
enclosure, utmost care shall be exercised in proper 
system design. 

5.3 Though exposure to the concentration levels of 
oxygen ( 1 to 15 percent by volume respectively) is 
normally considered to produce a negligible risk to 
the personnel, certain provisions like personnel training, 
warning signs, pre-discharge alarms, and discharge 
inhibit switch shall be put in place. In addition, adequate 
ventilation facilities shall be available to exhaust the 
trapped gases following extinguishment process. 

5.4 Minimum safety precautions and safety limits 
that are associated with the use of IG 55 are as shown 
in Tables 5 and 6. Since a fire can be expected to 
consume oxygen and form decomposition products, 
personnel shall treat any fire sitiiation as an emergency 
and promptly exit the enclosure. 

5.5 Additional provisions as shown in Table 7 
shall apply to account for failure of safeguards 
( see 5.1 to 5.4 ) to prevent accidental exposures to 
the human present within the enclosure. 

6 ENCLOSURE STRENGTH AND VENTING 
FACILITIES 

6.1 Venting may be provided at levels as high as 
possible in the enclosure strength and allowable 
pressures for average enclosures may be in conformity 
with the 6.2. The building requirements for the type 
of enclosure and free venting required can also be 
calculated from the relevant specifications, 

6.2 Free venting facilities shall be provided for 
the enclosure and the equations for determining the 
venting area required shall be as follows: 



a) S^ = CS, + S^ 



( lOO-C) 
100 



where 

S^ = specific vapour volume of IG 55/air 
mixture at 20°C; 

= specific vapour volume' of IG 55 at20°C 
( equals 0.708 1 mVkg, see Table 8 ); 

specific vapour volume of air at 20'^C 
( equals 0.830 mVkg ); and 

final injected concentration of IG 55 
within the enclosure [ see 7.3.2(d) ]. 



S, = 



s. 



c 



IS 15506:2004 



x» 

UJ 
QC 
3 
C/) 
CO 
LU 

cc 

CL 



210 

200 
190 

180 

170 

160 

150 

140 

130 
120 























/ 




















y 


y 
















y\ 


y 


















y 


y 


















y 


/^ 
















y 


/• 


















\y 


X 


















y 




















x" 























-20 -10 10 20 30 40 50 60 70 80 90 
TEMPERATURE ''C 



Fig. 1 Temperature/Pressure Graph for IG 55 Pressurized to 1 5 and 20 MPa at 1 5°C 

Tables Minimum Safety Precautions 

{Clauses A) 



SI No. IG 55 Injected Concentration 



(I) 

i) 
ii) 



iii) 



Percent by Volume 



(2) 







Rcquh'c 


nicnts 




Inhibit S> 


A' itch 


Egress in 30 s 




Safety 


Lock -off 


and Time 


Delay 


Max 




Interlock 


Valve 


(3) 




(4) 




(5) 


(6) 


V 




Not required 




Not required 


Not required 


V 




V 




V 


Not required 



Up to NOAEL (43 percent) 

Between NOAEL and up to 
LOAEL ( 43 percent and 
52 percent ) 

Above the LOAEL 

( 52 percent ) 

*Concentration levels above LOAEL are not permitted in occupied areas and question of degress does not arise 



V 



V 



V 



Table 6 Safety Limits 

{Clause 5 A) 



\ No. 


Safety Limit 


IG 55 Design 
Concentration'' 


(1) 


(2) 


(3) 


i) 


NOAEL 


43 


ii) 


LOAEL 


52 


'^Percentage by volume. 







Residual Oxygen 
Concentration'* 

(4) 

12 

10 



b) A^{QS,)x{lPS^r''' 
where 
A = venting area required, in m^; 

Q = maximum IG 55 flow within enclosure 
in kg/sec ( Total weight/discharge 
duration, in seconds ); and 

P = maximum allowed overpressure within 



the enclosure, that is, 500 pascals. 

7 EXTINGUISHING AGENT SUPPLY 

7.1 Quantity 

a) The amount of the IG 55 in the system 
shall be at least sufficient for the largest 
single hazard protected or group of 



18 15506:2004 



Table 7 Human Exposure to IG 55 Agent 

( Clause 5.5 ) 



S! No. 


Exposure 




IG 55 [njcctcd Agent 


Concentration ( Pci 


xent) 




Up to 43 Between 43 
and 52 




Between 52 
and 62 


More Than 
62 


(1) 


(2) 




(3) (4) 




(5) 


(6) 


i) 


Oxygen concentration 
in sea-level equivalent 


( percent ) 


12 Between 
12 and 10 




Between 
10 and 8 


Less than 
8 


ii) 


Status of space 




Normally Normally 
Occupied Occupied 




Normally 
unoccupied 


Normally 
unoccupied 


iii) 


Exposure time 




Not more Not more 
than 5 min than 3 min 




Not more 
than 30 s 


No exposure 
permitted 



communicating hazards that are to be 
protected simultaneously. 

b) Where required, the reserve quantity 
should be same as that of main supply as 
in 7.1(a) above. However if replenishing of 
IG 55 supply takes more than 7 days at 
the site of installation, advice may be sought 
from the authority concerned on the quantity 
to be kept available as reserve. 

c) Reserve supply where provided and the 
main supply should be permanently 
connected to the distribution piping and 
arranged for quick and easy changeover to 
enable uninterrupted protection. 

d) The quantity of the IG 55 required shall 
be further adjusted to compensate for any 
special conditions, such as unclosable 
openings, forced ventilation, the free volume 
of air receivers that may discharge into 
the risk, altitude ( substantially above or 
below sea level ) or any other causes for the 
extinguishant loss. 

7.2 Total Flooding Quantity 

a) The amount of IG 55 required to achieve 
the design concentration shall be 
calculated from the following equations 
and this figure shall need further 
adjustment as stated in 7.1(d). 

V 100 



M- 2.303 



x^^s><Log,o 



C 



S ' ^'" 100- 

where 

M = total flooding quantity, kg; 

C = design concentration, percent by 
volume; 

V = net volume of the hazard, m"^; 



= /vj -\- Kji T ), where K^ and Kj are 
constants specific to the agent used 
and T is minimum temperature inside 
enclosure; and 



V^ = specific volume of superheated agent 
at2lX,nvVkg. 

Specific volume constants for the IG 55 gas 
are K^ = 0.659 8 and A", = 0.002 42. IG 55 is a 
non-liquefied gas at 15 MPa. It may also be 
noted that this equation provides an allowance 
for the normal leakage from a tight enclosure. 

b) The agent requirement per unit volume of 
protected space can also be calculated by 
using the Table 8 for various levels of 
concentration corresponding to the 
temperature within the protected enclosure. 

NOTE — Quantity of the agent shall be the highest 
of the values calculated from the provisions contained 
in 7.2(a) and 7.2(b) above. 

7.3 The actual quantity of IG 55 gas storage required 
and the resultant residual oxygen concentration 
produced shall be determined in the following manner, 
which shall further subject to changes for pressure 
change due to elevation ( see lA ). 

7,3.1 Enclosure Volumes 

The net enclosure volumes are calculated using the 
following equations: 



a) 


V.= ^,-^'s 


b) 






where 




^M'i\ ^ maximum net volume of the enclosure 



Mm 



=^ gross volume of enclosure, m'; 

^volume of the structural/similar 
permanent objects in the enclosure 
that gas can not permeate, m\ 

= minimum net volume of enclosure 
considering the maximum anticipated 
volume of the occupancy related to 
the objects in the enclosure, m-\; 
and 



IS 15506 :2004 



Table 8 Total Flooding Quantity ( IG 55 ) 

( Clause 7.2 ) 



SI No. 


Temperature 


Specific 




Mass 


Requirements of IG 55 per 


Unit Voh 


ime of 






r 


Vapour 

Volume 

mVkg 

S 




Hazard, kg/Vj,,,^.,,,^,,,.^ Design Concentra 
( Percent by Volume) 


tion 






34 


38 


42 


46 


50 


54 


58 


62 


(I) 


(2) 


(3) 


(4) 


(5) 


(6) 


(7) 


(8) 


m 


(10) 


(11) 


i) 


-40 


0.568 17 


0.524 


0.603 


0.688 


0.778 


0.875 


0.980 


1.095 


1.221 


ii) 


-35 


0.563 24 


0.513 


0.591 


0.673 


0.761 


0.856 


0.959 


1.072 


1.196 


iii) 


-30 


0.587 32 


0.503 


0.579 


0.659 


0.746 


0.839 


0.940 


1.050 


1.171 


iv) 


- 25 


0.599 40 


0.493 


0.567 


0.646 


0.731 


0.822 


0.921 


L029 


1.147 


V) 


-20 


0.611 48 


0.483 


0.556 


0.633 


0.716 


0.806 


0.903 


1.008 


1.125 


vi) 


- 15 


0.623 55 


0.474 


0.545 


0.621 


0.702 


0.790 


0.885 


0.989 


1.103 


vii) 


- 10 


0.635 63 


0.465 


0.535 


0.609 


0.689 


0.775 


0.868 


0.970 


1.082 


viii) 


-05 


0.647 71 


0.456 


0.525 


0.598 


0.676 


0.761 


0.852 


0.952 


1.062 


ix) 





0.659 79 


0.448 


0.515 


0.587 


0.664 


0.747 


0.837 


0.935 


1.042 


X) 


5 


0.671 86 


0.440 


0.506 


0.576 


0.652 


0.733 


0.822 


0.918 


1.024 


xi) 


10 


0.683 94 


.0.432 


0.497 


0.566 


0.640 


0.720 


0.807 


0.902 


1.006 


xii) 


15 


0.696 02 


0.424 


0.488 


0.556 


0.629 


0.708 


0.793 


0.886 


0.988 


xiii) 


20 


0.708 10 


0.417 


0.480 


0.547 


0.619 


0.696 


0.779 


0.871 


0.97 i 


xiv) 


25 


0.720 17 


0.410 


0.472 


0.538 


0.608 


0.684 


0.766 


0.856 


0.955 


xv) 


30 


0.732 25 


0.403 


0.464 


0.529 


0.598 


0.673 


0.754 


0.842 


0.939 


xvi) 


35 


0.744 33 


0.397 


0.456 


0.520 


0.588 


0.662 


0.742 


0.828 


0.924 


xvii) 


40 


0.756 41 


0.390 


0.449 


0.512 


0.579 


0.651 


0.730 


0.815 


0.909 


xviii) 


45 


0.768 48 


0.384 


0.442 


0.504 


0.570 


0.641 


0.718 


0.802 


0.895 


xix) 


50 


0.780 56 


0.378 


0.435 


0.496 


0.561 


0.631 


0.707 


0.790 


0.881 


XX) 


55 


0.792 64 


0.373 


0.429 


0.488 


0.553 


0.622 


0.696 


0.778 


0.868 


xxi) 


60 


0.804 71 


0.367 


0.422 


0.481 


0.544 


0.612 


0.686 


0.766 


0.855 


xxii) 


65 


0.816 79 


0.362 


0.416 


0.474 


0.536 


0.603 


0.676 


0.755 


0.842 


xxiii) 


70 


0.828 87 


0.356 


0.410 


0.467 


0.528 


0.594 


0.666 


0.744 


0.830 


xxiv) 


75 


0.840 95 


0.351 


0.404 


0.460 


0.521 


0.586 


0.656 


0.733 


0.818 


xxv) 


80 


0.853 02 


0.346 


0.398 


0.454 


0.513 


0.578 


0.647 


0.723 


0.806 


xxvi) 


85 


0.865 10 


0.341 


0.393 


0.448 


0.506 


0.569 


0.638 


0.713 


0.795 


xxvii) 


90 


0.877 18 


0.337 


0.387 


0.441 


0.499 


0.562 


0.629 


0.703 


0.784 


xxviii) 


95 


0.889 26 


0.332 


0.382 


0.435 


0.493 


0.554 


0.621 


0.693 


0.773 


xxix) 


100 


0.901 33 


0.328 


0.377 


0.430 


0.486 


0.547 


0.612 


0.684 


0.763 



F == volume of the occupancy related 
objects in the enclosure that gas can 
not permeate, for example, furniture 

fittings, etc, m^\ 

7.3.2 IG 55 Parameters 

The required IG 55 gas quantity, number of 
cylinders, actual injected concentration, etc, are 
calculated using the following equations: 



a) IG 55 agent quantity ( theoretical ) 
where 



(1) 



Mji^ == theoretical IG 55 quantity, m"^; 

^Max ^ maximum net volume of the enclosure, 
m^; and 

C, = appropriate injected concentration. 

b) IG 55 containers 

The number of containers required shall be 
as follows after rounding off as appropriate: 

N-MJM^ (2) 

where 

yV ^ number of containers; 

M^= theoretical IG 55 quantity, m\ and 



IS 15506:2004 



Mp = Quantity of IG 55 agent per container. 

Standard containers with standard filling 
pressures shall be adopted to facilitate 
logistics. 

c) Actual quantity of IG 55 agent 

The actual quantity of the agent is determined 
as per the equation below: 

(3) 



e) 



M^ = TV times M^ 

where 

M^ = actual quantity of IG 55 storage, m"^; 

N = number of containers; and 

M^ = quantity of IG 55 agent per container, 
m\ 

d) Actual IG 55 injected concentration 

The actual injected concentration of the agent 
based on the actual quantity of the IG 55 agent 
storage is calculated as below: 

■.. (4) 



where 



A Max 



C^j = actual IG 55 injected concentration; 

Mj^ ^ actual quantity of IG 55 storage, m\ 
and 



Max 



maximum net volume of the enclosure, 



m' 



Lastly, it is required to adjust the number of 
IG 55 agent containers, where necessary, by 
compensating for ambient pressure change 
due to location elevation as per 7.4 and round 



off the number as before. The equation in 
such cases will be as follows: 

N^= N times atmospheric correction factor 



where 

A^ = initial number of containers. 



yV| = adjusted number of containers, and 



7.4 Atmospheric Correction Factors 

It shall be necessary to adjust the actual IG 55 agent 
quantity for altitude effects. Depending upon the 
altitude, atmospheric correction factor shall be applied 
as per Table 9. The adjusted IG 55 agent quantity is 
determined by multiplying the number of IG 55 
containers by the ratio of average ambient enclosure 
pressure to standard sea level pressure. 

8 CONCENTRATION REQUIREMENTS 

8.1 Fire Extinguishing Concentration 

The minimum design concentration of the IG 55 
agent for Class A surface fire hazards shall be the 
extinguishing concentration with a loading of 
20 percent as a safety factor (29.1 + 20 percent = 
35 percent). 

The minimum design concentration of the IG 55 
agent for Class B fuel hazards shall be the 
extinguishing concentration with a loading of 
30 percent as a safety factor. 

8.2 Combustible Solids 

The minimum injected concentration of IG 55 agent 



Table 9 Atmospheric Correction Factors 

( Clause lA ) 



SI No. 


Equivs 


ilent Altitude 


Enclosure Pressure 


ni 




mm 


mm Hg 


(1) 




(2) 


(3) 


i) 




-920 


840 


ii) 




-610 


812 


iii) 




-300 


787 


iv) 







760 


V) 




300 


733 


vi) 




610 


705 


vii) 




920 


678 


viii) 




1 220 


650 


ix) 




1 520 


622 


X) 




1 830 


596 


xi) 




2 130 


570 


xii) 




2 440 


550 


xiii) 




2 740 


528 


xiv) 




3 050 


505 



Atmospheric Correction Factor 

(4) 

1.11 

1.07 

1.04 

1.00 

0.96 

0.93 

0.89 

0.86 

0.82 

0.78 

0.75 

0.72 

0.69 

0.66 



IS 15506: 2004 



for surface type Class A risks shall not be less than 
40 percent by volume which yields, on a free efflux 
basis, a residual oxygen concentration of 14 percent 
by volume in the enclosure. 

9 APPLICATION RATE AND DISCHARGE 
TIME 

9.1 Rate of Application 

The design application rate shall be based on 
the quantity of IG 55 (MA) [ see 7.3.2(c) ] for the 
desired concentration ( see 8.1 or 8.2 as the case 
may be ) and for the time allotted to achieve the 
design concentration ( see 9.2 ). The oxygen 
concentration, however, shall be within the limits as 
specified in 5.3. 

9.2 Duration of IG 55 Discharge 

a) The discharge time period is defined as the 
time required to discharge from the nozzles 
95 percent of the agent mass at 2 1 °C, necessary 
to achieve the minimum design concentration 
based on a 20 percent safety factor for flame 
extinguishment. 

b) The minimum theoretical injected 
concentration, that is, 34 percent by volume 
shall be achieved within 1 min and the actual 
injected concentration ( that is the above plus 
a suitable safety factor, adjustment for 
container rounding off) shall be achieved 
within 2 min. 95 percent of the minimum 
design quantity of the agent shall be released 
within 60 s. 

c) Flow calculations performed in accordance 
with 12, or in accordance with the listed 
pre-engineered systems, shall be used to 
demonstrate the discharge time require- 
ments stated above. 

d) When an extended discharge is desired to 
maintain the design concentration for the 
specified period of time, additional quantities 
of agent can be applied at a reduced rate. The 
initial discharge shall be completed within 
the limits as specified above. Performance 
of the extended discharge shall be 
demonstrated by test. 

e) Where containers are situated remote from 
the protected enclosure, extended transit time 
will be apparent. Authorities concerned shall 
be consulted before locating the containers 
in such cases. 

9.3 Retention Time 

Following the discharge of the agent into the 
enclosure, at least 80 percent of the design 
concentration (or inerting concentration as the case 



may be) shall prevail when measured after 10 min of 
discharge ( see Annexes C and D of IS 1 5493 ). 

10 STORAGE CONTAINERS 

The IG 55 storage containers shall comply with 
the following in addition to various requirements 
contained in IS 15493. 

a) The containers used in IG 55 systems shall 
be seamless cylinders conforming to IS 7285 
designed, fabricated, inspected, certified and 
stamped in accordance with the requirements 
of Chief Controller of Explosives, Nagpur. 

b) The design pressure shall be suitable for the 
maximum pressure developed at 65 °C or at 
the maximum controlled temperature limit. 

c) The storage containers shall have reliable 
means of indicating their pressure. 

d) The storage containers shall have reliable 
means of indicating the variation of container 
pressure with temperature. A pressure/ 
temperature chart attached to the container 
is acceptable. 

e) The requirements of authorities having 
jurisdiction for containers may take 
precedence over the requirements of this 
standard, if their specifications are more 
stringent. 

11 DISTRIBUTION SYSTEM 

The IG 55 distribution system shall comply with 
the following in addition to various requirements 
contained in IS 15493. 

11.1 Piping Network 

a) The piping shall withstand the maximum 
expected pressure at the maximum storage 
temperature and shall be in accordance with 
IS 15493. 

b) Carbon steel pipes and fittings shall be 
galvanized inside and outside or otherwise 
suitably protected against corrosion. 
Stainless steel pipes and fittings may be used 
without corrosion protection. 

11.2 Piping Fittings 

a) Pipe fittings shall comply with the 
requirements given in IS 15493. 

b) Fittings shall be selected according to the 
wall thickness or schedule number of the pipe 
to which they are intended to be fitted. 

11.3 Pipe Sizing 

Pipe sizing is a complex issue, particularly when too 
small a bore results in excessive pressure losses while 



18 15506:2004 



too large a bore reduces the flow velocity. This also 
may result in excess pressure drops and lower flow 
rates. Table 10 may be used as a guide to estimate 
pipe sizes. The sizes can be checked using an approved 
computer flow calculation programme. 

11.4 Nozzle Placement 

a) The type of nozzles selected, their number 
and placement shall be such that the 
design concentration will be established in 
all parts of the protected enclosure and such 
that the discharge will not unduly splash 
flammable liquids or create dust clouds that 
could extend the fire, create an explosion, or 
otherwise adversely affect the contents or 
the integrity of the enclosure. 

b) Nozzles shall be selected and located to 
protect an area less than its area of coverage. 
The area of coverage to the type of nozzle 
shall be so listed for the purpose. 

c) Maximum nozzle height above floor level 
for a single row of nozzles is 3.5 m. Where 
ceiling height ( of the protected enclosure ) 
exceeds 3.5 m, an additional row of nozzles 
shall be provided for uniform and faster 
distribution of the agent within the 
enclosure. 

d) Minimum nozzle height above the floor 
level of the hazard shall be 0.2 m. 

e) In case of enclosures having no false 
ceiling, nozzles can be located on the ceiling 
anywhere within 0.5 m to 5 m from the walls 
In case of enclosures having false ceilings, 
deflector shields shall be used with each 
nozzle and also nozzles shall be so located 
( with an anticipation of dislodgement of false 
ceiling materials or any movable objects in 
the path of discharge ) to prevent any damage 
thereto. 

f) Nozzles shall be provided in all the 
concealed spaces, floor voids, ceiling voids, 
etc, besides the main area within the 
protected enclosure. 

g) Selecting the number of nozzles in a system 
shall take into account, the shape of the 
enclosure ( area and volume ), shape of the 
void ( raised floor, suspended ceiling ). 
Installed equipment in the enclosure/void 
( chimney effect ), allowed pressure at the 
restrictor ( pipe quality ), obstructions, which 
may affect the distribution of the discharged 
agent and architectural considerations. 

h) In hazards having suspended ceiling, 
consideration shall be given for having 
nozzles installed in the ceiling void 



( simultaneous discharge ) in order to 
equalize the pressure during discharge, thus 
reducing the risk of unnecessary damaging 
ceiling tiles, etc. 

j) in hazards having raised floor ( not gas- 
tight ) consideration shall be given for having 
nozzles installed in the floor void 
( simultaneously discharge ) in order to 
equalize the pressure and obtain 
extinguishing concentration below the 
floor. 

k) In hazards having suspended ceiling, 
nozzles for protecting rooms void shall be 
installed in such a way that the jets from the 
nozzles do not damage the ceiling plated 
excessively during discharge, that is, the 
nozzles to be positioned vertically with the 
discharge holes free of the ceiling tiles and/ 
or Escutcheon plates. For light weight ceiling 
tiles, it may be recommended to securely 
anchor tiles for a minimum of 1 .5 m from each 
discharge nozzle. 

m)The maximum distance between nozzles 
should not exceed 6 m and the maximum 
distance to wall/partition should not exceed 
3 m. 

Table 10 Pipe Sizes versus Flow Rate 
(Informative) 

iClcnise\\3) 



SI 


Pipe Size 


Schedule 40 


Schedule 80 


No. 


mm 


kg/min 


kg/min 


(1) 


(2) 


(3) 


(4) 


i) 


12 


1-30 


1-23 


ii) 


20 


30-50 


23-43 


iii) 


25 


50-85 


43-72 


iv) 


32 


85-150 


72-130 


V) 


40 


150-200 


130-175 


vi) 


50 


200-335 


175-295 


vii) 


65 


335-475 


295-425 


viii) 


80 


475-740 


425-660 


ix) 


100 


990-1 275 


890-1 150 


X) 


125 


i 275-2 000 


1 150-1 820 


xi) 


150 


2 000-3 000 


I 820-2 600 



12 HYDRAULICS OF THE SYSTEM 

12.1 An approved hydraulic calculation method 
shall be employed to predict pipe sizes, nozzle pressure, 
agent flow rate, discharge per nozzle and the discharge 
time. 

12.2 The various parameters described in 7.3.1, 7.3.2, 
9.1 and 9.2 shall be considered to determine the 
following minimum limits of accuracy. 



IS 15506:2004 



12.3 The weight of agent predicted by flow calculation 
to discharge from the nozzle should agree with the 
total weight of agent actually discharged from each 
nozzle in the system within a range of -5 percent to 
+ 10 percent of actual prediction. 

12.4 The discharge time predicted by the flow 
calculation method should agree with the actual 
discharge time from each nozzle in the system within 
a range of ± 5 s. 

12.5 The accuracy of the calculated nozzle 
pressures versus actual pressures at each nozzle 
should be such that actual nozzle pressures in an 
installation will not fall outside the range required 
for acceptable nozzle performance. 

12.6 The nozzle pressure should not fall below 
the minimum or above the maximum nozzle pressure 
required for the nozzle to uniformly distribute the 
agent throughout the volume for nozzle's discharge 
is to protect. 

13 COMMISSIONING AND ACCEPTANCE 
TESTING 

13.1 Criteria for Acceptance 

The completed IG 55 total flooding system shall be 
commissioned in accordance with IS 15493 and the 
system's performance proved by at least one of the 
following methods: 

a) It is not normally recommended to 
conduct full-scale discharge test of IG 55 total 
flooding systems. Where the authorities 
concerned insist on full-scale discharge test, 
the tests shall be conducted in accordance 
with 14. 

b) Where a full discharge test using IG 55 is not 
insisted by the authorities concerned, the 
following procedure shall apply: 

1) Subject the distribution system to a 
hydrostatic pressure test of 1.50 times 
the-calculated pipework's maximum 
developed storage pressure at 55''C, then 



purge the system to remove moisture and 
prove free passage. 

2) Subject the protected area to an 
enclosure integrity test in accordance 
with IS 15493. 

13.2 Commissioning Certification 

When the system commissioning is completed 
the installation agency shall issue a typical test 
certificate. 

13.3 Where the system fails to comply with various 
provisions as stated above, the fault shall be rectified 
and, if necessary, the system retested. 

14 IG 55 FULL SCALE DISCHARGE TEST 
PROCEDURE 

14.1 This shall be in accordance with IS 15493. 

14.2 Recommissioning 

Restore all systems to a fully operational status. 

14.3 Reporting 

The following shall be reported: 

a) Information identifying the system shall 
include: 

1) Installation, designer and contractor; 

2) Enclosure identifications; 

3) Enclosure temperature prior to discharge; 

4) Oxygen and carbon dioxide residual 
concentrations; and 

5) Position of sampling points. 

b) Date and time of test. 

c) Discharge time. 

d) Concentration levels at each sampling point 
at 2 min and 1 min from the commencement 
of discharge. 

e) System deficiencies. 

f) Reference to this test method in accordance 
with IS 15493.